Gene Silencing in Fruit Crops

1. M K SAINI
1
Presented by:
Mandeep Kaur
L-2018-A-35-D
PhD Fruit Science
Gene Silencing in Fruit Crops
Presented to:
Dr H S Dhaliwal
Dr Monika Gupta
Dr Rachna Arora

2. M K SAINI
Gene Silencing
Gene silencing is the regulation of gene expression in a cell to prevent the
expression of a certain gene.

3. M K SAINI
Virus-induced Gene Silencing (VIGS)
• VIGS is a post-transcriptional gene silencing technique.
• VIGS: RNA-mediated silencing of endogenous plant genes initiated by
recombinant viral vectors.
• It permits knockdown of GOI & observation of elicited phenotypes within 3-4 weeks.
Zhang et al (2019) China

4. M K SAINI
Precocious flowering of juvenile citrus induced by a
viral vector based on Citrus leaf blotch virus
• Long juvenile period => Major breeding constraint.
• Citrus leaf blotch virus-based vector (clbvINpr-AtFT and clbvINpr-CiFT).
• Flowering Locus T (FT) gene - A. thaliana (AtFT) or citrus (CiFT).
• Flowering (within 4-6 months).
(a) non-inoculated adult plant and
(b) Inoculated juvenile
Graft inoculation with infected patches of
(clbvINpr-AtFT and clbvINpr-CiFT) vector
Velazquez et al (2016) Spain

5. M K SAINI
Reduced generation time of apple seedlings by viral
vector based on apple latent spherical virus
• Long juvenile phase => Major breeding constraint.
• VIGS - Apple Latent Spherical Virus (ALSV) Vector (ALSV-AtFT/MdTFL1).
• Arabidopsis Flowering Locus T (AtFT) gene.
• Terminal Flower 1 gene (MdTFL1).
• Biolistic inoculation of apple cotyledons. Apple seeds - 4 °C before use.
• Simultaneous expression of AtFT gene & silencing of MdTFL1 gene.
• Flowering within 1.5–3 months.
Continuous flowering in infected apple seedling at 1.5, 3, 7 months post-inoculation
Yamagishi et al (2014) Japan

6. M K SAINI
RNAi - mediated silencing of PPO genes in Arctic Apple
• Browning is mediated by polyphenol oxidase (PPO).
• Polyphenol Oxidase + O₂ → Melanin (Brown Color).
• Non browning apple – Unachievable by conventional breeding methods.
• RNAi construct to silence four PPO genes in apples.
• Non-browning apples - ‘Arctic apple’.
• Arctic® Golden & Arctic® Granny - Approved by US and Canadian regulatory agencies.
• Arctic® Gala and Fuji are also in the works.
Arctic® Granny
Arctic® Golden
Kim et al (2015) Korea

7. M K SAINI
Conclusion & Future Prospects
• Biotechnology has brought great opportunities and
prospects for overcoming problems of conventional
breeding.
• However, biotechnology as transgenic breeding or genetic
manipulation cannot replace conventional breeding but it is
and only is a supplementary addition to conventional
breeding.
• Therefore, integration of biotechnology into conventional
breeding programs will be an optimistic strategy for fruit
crop improvement in the future.

8. M K SAINI